Hello all,

Does anyone know how to construct a multiplier circuit using just logic gates?? Say an 4x4 bit or an 8x8 bit multiplier?

Thanks

 

If your multiplier is by 4 or 8 you can use a bit shift circuit, but if you want a broader range then I'm not sure.

 

I would use an EPROM, but I'm lazy.

 

If your multiplier is by 4 or 8 you can use a bit shift circuit, but if you want a broader range then I'm not sure.

No, a bit shift circuit is too limited. I need a circuit that would multiply any pair of numbers (bit sequences).

 

Just some musings:
You might be able to use
* A 16-bit shift-left register with only the lower 8 bits programmable -- the upper 8 bits are always loaded with zeros.
* An 8-bit shift-right register with the output fed to
* a 16-bit accumulator. The accumulator adds in the value of the 16-bit register whenever the output from the 8-bit register goes high, OR when the 16-bit register is initially loaded.
* A clock that generates 8 pulses and stops. It clocks both registers.
* Assorted switches, resistors, and LEDs for input, run, and output.

Timing and race conditions are left for the poor student to puzzle his or her head over.

--Rich

 

I would use an EPROM, but I'm lazy.

I second thingmaker3's EPROM approach. A 4-bit by 4-bit multiply should be fairly easy to manually create with such an approach. It has the added advantage of being very fast.

hgmjr

 

The EPROM approach would be a good one. But, I can't use it in my project. The point is to use just logic gates.

Here is on approach that I found in Wikipedia:

http://en.wikipedia.org/wiki/Binary_multiplier


Suggestions?? Comments??

Thanks....

 

The EPROM approach would be a good one. But, I can't use it in my project. The point is to use just logic gates.

Oh, those nasty professors! Always making someone work hard to remember their lessons.

I guess I'd go with counters. Increment count by fist term, and repeat a number of times equal to second term.

Or use an adder and a counter. Add first term to itself a number of times equal to second term.

Aw, heck. Who are we kidding? I'd argue with the professor until I was blue in the face that EPROMs are just fancy latches and all latches are made from gates!

 

Try googling "Wallace Trees"

 

Oh, those nasty professors! Always making someone work hard to remember their lessons.

I guess I'd go with counters. Increment count by fist term, and repeat a number of times equal to second term.

Or use an adder and a counter. Add first term to itself a number of times equal to second term.

Aw, heck. Who are we kidding? I'd argue with the professor until I was blue in the face that EPROMs are just fancy latches and all latches are made from gates!

Yeah, that's a good argument. But now, If I use a counter, I would have to implement that counter with logic gates. No IC's are allowed basically. So what type of scheme can I use that implements the least # of gates?

 

Try googling "Wallace Trees"

I will do that.

 

also check on dadda multiplier by googling

moz

 

Go with PapaBravo's advice. I was quite impressed with what I found when I did. Also google "Dadda multiplier." Be sure to give PapaBravo a hearty "thank you."

 

The respect of one's peers is a precious thing to be savored and enjoyed. Thank's for those kind words.